Imaging method

ABSTRACT

Images are formed on direct positive photographic material in a single white-light exposure through the use of a master sheet which consists essentially of a selectively transmissive filter layer which allows transmission only of longer wave length light which is effective in reversing the prefogged direct positive material, and indicia disposed with respect to the filter layer to form in the master substantially totally opaque elements and substantially totally white light transmissive elements. Normal photographic development of the direct positive material after exposure provides positive images of equal intensity corresponding to the opaque and transparent indicia elements.

United States Patent [151 3,642,477

Trusheim et al. 1 Feb. 15, 1972 [54] IMAGING METHOD 7 3,526,507 9/1970 lshikawa ..96/45.2

72 l t :Fr kM.T hel 01th t;

l 1 men ors 1? ski, s l i 5. Lwamr c Primary Exammer-Nonnan G. Torchm Assistant Examiner-Judson R. Hightower [73] Assignee: Keulfel & Enter Company, Morristown, Attorney-J. Russell Juten, Peter F. Willig, Lionel N. White NJ. and Milford A. Juten [22] Filed: Apr. 24, 1969 57 ABSTRACT [21 1 Appl- 819,067 images are vformed on direct positive photographic material in a single white-light exposure through the use of a master sheet 52] u.s.c| 96145.2, 96/27,96/64 which mists essentially Of a Selectively transmissive film [5] |m C| G03c 5/32 layer which allows transmission only of longer wave length 58 Field of Search ..96/27, 45.2, 64 which is effective in reversing the Prefmed tive material, and indicia disposed with respect to the filter "mes layer to form in the master substantially totally opaque ele- [56] Rate Cited ments and substantially totally white light transmissive ele- UNlTED STATES TE T ments. Normal photographic development of the direct positive material after exposure provides positive images of equal 2,912,325 1 1/1959 intensity corresponding to the opaque and transparent indicia elements. 3,124,458 3/1964 3,178,997 4/1965 4Claims, 1 Drawing Figure WHITE LIGHT SOURCE 30 I6 ix \1 I6 14 FILTER LAYER MASTER IO V/ A W 12 TRANSPARENT 132 g g 32; 34 BASE 2 24 EMULSION N N a w J LAYER 22 BASE DIRECT POSITIVE SHEET 20/ DEVELOP PATENTEDFEB 1 5 I972 WHITE LIGHT SOURCE 3O -lz TRANSPARENT BASE 24 EMULSION LAYER 22 BASE I4 Fl L W J LTER LAYER DEVELOP 7 W/fil MASTER IO DIRECT POSITIVE SHEET 20/ N VliNlORS FRANK M, TFIUSHEIM BY WALTER C. ZANIEWSKI A T TORNEY IMAGING METHOD BACKGROUND OF THE INVENTION Direct positive photographic materials, are well known in the field of image reproduction, particularly in the graphic and cartographic arts. Such direct positive materials function generally according to the HerschelEffect wherein a silver halide photographic emulsion having uniformly distributed fogging centers or nuclei reverts toan unfogged state upon exposure to light of a wave length substantially greater than the peak sensitivity wave length of the silver halide emulsion.

The term Herschel Effect" might be. considered to be somewhat of a misnomer with respect to modern. direct positive photographic materials since the prefogging of the photographic material was achieved by- Herschel (1839) by means of an overall light exposure, whereas presentcommercially available direct positive photographic papers are prefogged and presensitized chemically through the use of reducing agents and dyes such as the Pinakryptol dyes. Regardless of the process employed to createthe fogging nuclei, however, the'behavior of the resultingdirect positive photographic material remains such as to become defogged or rendered incapable of image-forming development upon exposure to longer wave length light, as in the yellow and red ranges of the white-light spectrum.

As used in a simple graphic artimaging process, direct positive material, such as a sheet of direct positive paper, is exposed under a positive master; for example atransparent sheet bearing opaque indicia, to yellow light 'suchas obtained by passing a carbon arc beam through a yellowfilter. Continued exposure of this photographic material completely destroys the prefogged nuclei in thephotographicemulsion in all areas which are not protected by the opaque indicia of the master and subsequent development in a common photographic developer solution followed by fixing provides apermanent positive copy of the opaque indicia of the original master.

The direct positive photographic sheet is useful also in the preparation of composite images; however, prior to the present invention, photocomposition methods required repeated exposures, extended make-ready time, and continued attention to precise registration. For example, in the cartographic art it is general practice to create separate graphic masters of the various types of features appearing on a given map; that is, streams and waterways, roads and highways, and topographic features are generally prepared on separate archival plates with each such plate bearing its own appropriate symbolic nomenclature and indicia.

The preparation of these archival plates has generally been accomplished by various photocomposition procedures from hand-drawn originals through multiple steps ofpositive and negative photographic image regeneration. A medium for the preparation of original drawings of topographic features and the like which has received great acceptance in the field is the scribe coat which generally comprises a transparent base having a heavily-pigmented, readily-removable opaque coating. Some such pigmented scribe materials are described in US. Pat. No. 2,999,016. Original drawings on such material are accomplished through the removal of portions of the opaque scribe coat to create a negative of the topographic or other land feature layout. Symbolic indicia and lettering are normally prepared separately in positive form on a transparent overlay sheet which is later combined in the photocomposition process with the negative master of the topographic layout.

The reversal characteristics of direct positive materials are particularly well adapted to the employment of such comparative .positive and negative photocomposition layouts and overlays. Prior to the present invention, the most practical method of composing an archival plate required the steps of exposing a directpositive sheet through the positiveindicia overlay to a relatively long-wave yellow .light thereby creating," by reversal, a latent image of the opaque indicia in the directpositive sheet. Immediately thereafter and prior to development, this initially exposed direct positive sheet was again exposed through the negative scribed master to a relatively short durationwhite-light exposure which creates a new silver-center latent image in the defogged areas of the direct positive sheet. Subsequent chemical development of the direct positive sheet results in apositive image of both the indicia and the topographic features.

The outstanding difficulty in this process is readily apparent when one considers that the scribed master must be located in precise registration with the latent indicia previously formed in the direct positive sheet. Such precise registration requires additional registration guides and close attention to handling. The excessive time required in make-ready and the multiple exposure steps further detract from the desirability of previous methods.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of photocomposition employing direct positive photographic materials and whichv comprises a single light-exposure step thereby obviating excessive make ready time, and precise overlay registration.

The method of the present invention employs as the medium for preparation of the original exposure master a material which has the selective light transmissive properties of a Herschel light filter. That is, the medium on which the topographic or. other features are carried transmits in its nonimage areas only the longer wave lengths of light, as in the yellow and red spectrum bands. Direct positive photographic material exposed to light from a carbon arc or xenon lamp source through such a master medium will be effectively reversed or defogged.

Symbolic indicia and lettering may be readily applied to the surface of the master medium by means of ink drawing or transfer lettering and form opaque indicia elements which are desired to be reproduced in the final composite master plate.

It has been discovered in the present invention that where portions of the light filtering element of the master medium are removed, thereby creating areas of total spectrum band transmission of light from a white-light source, extended white-light exposure 5 of the direct positive photographic material will result in the formation of developable silver centers. Although the formation of such developable centers may be the result of well known solarization or double reversal phenomena, a white light exposure of fogged direct positive material is a most uncommon procedure and the resulting formation of development centers wholly unexpected.

In accordance with the present invention topographic features are created in the filter master medium in negative form as by scribing away portions of a selectively transmissive scribe coating andsymbolic opaque indicia are applied to the medium to form an exposure master.

The resulting exposure master is placed upon a sheet of direct positive photographic material and the combination exposed to a white light source for a time sufficient to defog" the direct positive material in areas lying immediately beneath the light filter composition layer and the direct positive material is then subjected to chemical development. The resulting silver image on the developed direct positive material is located in areas corresponding to the opaque indicia and the transparent features of the original master.

DESCRIPTION OF THE INVENTION The drawing depicts the copying process of the present invention and with reference thereto the following is a specific description of the invention.

An original exposure master ltl is made up of a transparent base sheet 12 of polyester film,,glass or the like hearing on-its surface a coating of a selective light filter composition l4. The light filter layer'is preferably of a pigmented, scribable composition or a peelable film including appropriate dyes or colored pigments to render the composition transmissive of light wave lengths in the Herschel range," that is, in the spectrum band of wave lengths substantially longer than the peak wave length sensitivity of the direct positive photographic material to be employed. Open areas 16 represent portions of the filter layer 14 which are removed as by scribing or peeling and represent an original line drawing of topographic features and the like. Removal of the filter layer material from areas 16 creates in the master medium 10 open window areas which are substantially wholly transmissive of white light through the transparent base 12.

Upon the filter layer 14 and in appropriate relation to the basic scribed topographic features in the master are located opaque symbolic indicia or lettering 18 to complete the original exposure master. The symbolic indicia may be applied in India ink or adhesive transfer lettering, or may be photographically created on the filter layer or in a transparent overlay which is combined with the original drawing of the topographic features in the filter master medium prior to light exposure.

A sheet of direct positive photographic material 20 is shown disposed in underlying relationship to the original master 10. While the composite of master l and direct positive material 20 will normally be that of a contiguous association, these sheets are shown in the drawing as being separated to some degree for clarity in representation. The master and the copy sheet may be in face-to-back or face-to-face relation depending upon the form in which the master is prepared. In some instances a face-to-face combination is preferred in order to obtain clearer images. The direct positive material 20 is made up of a base 22 which may be opaque or transparent and a prefogged photographic silver halide emulsion 24. The direct positive material 20 may be any of the many commercially available direct positive photographic products. Such a material is Keuffel & Esser Co. Autopositive Film (43rd Edition Cat. No. 392843) which includes in the photosensitive layer a desensitizer such as a Pinakryptol or Safranine dye in a silver halide emulsion fogged with chemically-induced silver development centers or nuclei.

The direct positive material 20 shown in the drawing is depicted as having undergone various changes in the emulsion layer as a result of the light exposure according to the present invention. Only area 26 of the emulsion layer is in the original prefogged developable state characteristic of direct positive photographic material, the remaining areas having been changed to some extent by incident radiation as will be later described.

The combination of direct positive material 20 and the original master is exposed to white light from a source generally represented at 30. This light source may be any type ofsource normally used in the graphic arts, for example: a carbon are or xenon lamp, and will have substantial radiation throughout the visible light bands. White light from source 30 is shown as rays 32 which are completely absorbed by opaque indicia 18 and completely transmitted by open areas 16 in the master 10, passing through the transparent base 12 in substantially unattenuated form to incidence upon the emulsion 24 of the direct positive material 20. White light rays 32 which are incident upon the filter layer of master 10 are attenuated in such a manner that light rays 34 of preselected wave lengths are transmitted to emulsion 24 of the direct positive material 20. The wave length band of rays 34 is determined by the filtering dyes and/or pigments in filter layer 14 so as to have the appropriate Herschel effect upon the original direct positive emulsion 24.

The various states of the emulsion 24 of the direct positive material immediately after light exposure are depicted in the drawing. As previously noted, area 26 which was protected from all light by opaque indicia 18 remains in the original chemically prefogged state and is capable of chemical development to a silver image. Areas 27 lying beneath the filter layer areas of 14 of the master are exposed only to the longer Herschel effect" light rays 34 and are defogged from their original state and therefore bear no development centers. Application of chemical development solutions to areas 27 results in no silver image formation. Areas 28 of emulsion 24 lying beneath open areas 16 of the master original receive the entire band of white light emission of source 30 and are rendered, presumably by solarization or double reversal, highly concentrated in development centers. In some instances, areas 28 receive sufficient white light exposure to create a visible, developable printout image.

The final step in the process of the present invention is the chemical development of the exposed photographic material 20. Development is carried out in common commercially available chemical developing solutions and results in a finished print 40 having silver images 42 of substantially equal density corresponding to the transparent line features and opaque indicia in the original master 10. As in common photographic finishing processes, the developed print 40 may be chemically fixed, washed and dried to obtain a master of archival keeping quality.

PREFERRED EMBODIMENTS EXAMPLE 1 A scribe coat master medium was prepared in the following manner.

A dispersion of the following composition was ball-milled to coatable consistency and coated to a dry thickness of 0.6 mil on a 5.0 mil sheet of biaxially oriented polyethylene terepthalate film (in this and following examples all ingredient amounts are in parts by weight unless otherwise specified):

Alkyd resin (oil modified glycerol phthalate) 70 Calcium carbonate pigment 35 A20 orange pigment (Cl pigment orange 25) 5.0 Red Lake pigment (Cl pigment red 53) 15 Solvent (toluol, xylene, and/or ethyl I25 acetate) After application of the composition to the base sheet the coating was dried in a fiow of warm air to effect removal of solvent.

The resulting scribe coat master medium was greater than about 70 percent transmissive of light in the spectrum bands above 6,200 A. and transmitted substantially no light in the spectrum bands below 5,600 A.

Topographic map features were scribed in the resulting material, thereby forming a master of transparent lines in a background of the red scribe coat. The transparent areas of the scribe lines transmitted substantially all light in the spectrum bands between about 4,000 A. and 7,000 A. from a white light source.

To complete the preparation of an exposure master, letters and numerals were drawn on the surface of the scribe coat with India ink. The areas of these indicia transmitted substantially no light between about 4,000 A. and 7,000 A. EXAMPLE 2 A sheet of commercially available direct positive film (Keuffel & Esser Company Catalogue No. 39-2843) was placed in underlying contact with the master prepared according to example 1. The combination was exposed for three minutes at a distance of 0.5 m. to the light of a 3,500 watt xenon lamp. After exposure, areas of the direct positive film coating corresponding to the transparent scribed lines of the original were visible as a printout image. The exposed direct positive material was developed for 10 seconds in a commercially available direct positive emulsion developer solution, usually a high-contrast hydroquinone developer, and resulted in the development of dense black images corresponding to the transparent lines and the opaque ink lettering of the original described in example l. The print was fixed in ordinary hypo solution and washed and dried according to common procedures to provide a permanent solution.

EXAMPLE 3 A dispersion of the following composition was ball-milled to a coatable consistency and was coated and dried to a thickness Nitrocellulose 5.0 Alkyd resin 35 Calcium carbonate pigment ll Prussian blue pigment 9.0 (CI pigment blue 27) Chrome yellow pigment 4.0 (CI pigment yellow 34) Solvent 200 On the resulting dried coating was applied a ball-mill dispersion of the following composition to a dry thickness of about 0.6 mils:

Alkyd resin 4.0 Titanium dioxide pigment l2 Calcium carbonate pigment 6.0

Solvent The resulting scribe coat material exhibited a peak transmission of light of wave lengths between about 5,300 and 5,500 A.

A master original was prepared from this material by scribing away portions of the coating in the image of topographic features followed by the application to the surface of the scribe coat material of black opaque adhesive transfer lettering denoting symbolic indicia. The resulting master was substantially wholly transparent in the scribed line areas to light between about 4,000 A. and 7,000 A, and was substantially opaque to light in that range in the lettered areas. The resulting master was used to expose a sheet of direct positive photographic material as in example 2, the direct positive material having a peak sensitivity between about 4,600 and 4,800 A, The combination of the master and the direct positive material was exposed to a xenon lamp as in example 2 for a period of about 3.5 minutes and was developed, fixed and washed according to common photographic procedures to obtain a permanent image of dense black corresponding to the scribed lines and the opaque lettering ofthe master original. EXAMPLE 4 A scribed original was prepared as in example 1 employing a scribe coat medium of the following composition:

Nitrocellulose 5 Alkyd resin Calcium carbonate pigment Chrome yellow pigment 6.5 (Cl pigment yellow 34) Solvent 200 The scribe coat exhibited greater than about 35 percent transmission above 5,800 A. and substantially no light transmission below wavelengths of about 5,200 A.

Black opaque adhesive transfer lettering and India ink were employed to form opaque indicia on the scribe master of the original. The scribed and opaque indicia areas transmitted, respectively, substantially all and substantially no light between about 4,000 A. and 7,000 A.

The resulting master was employed to expose a sheet of commercially available direct positive material as in example 2, the exposure being for about 3 minutes to the xenon lamp. Subsequent development, fixing, washing and drying provided a permanent black image corresponding to the scribed lines and opaque lettering of the original.

EXAMPLE 5 A peelable coat master medium was prepared by coating a balLmill dispersion of the following composition on a sheet of biaxially oriented polyethylene terepthalate film to a dry thickness of about 0.6 mils:

The coated composition was dried to effect removal of solvents and resulted in a film which was self-sustaining and peelable from the polyester base sheet.

To prepare a master original common methods were employed to remove desired portions of the peelable coating and thereby form line and open window images in the material. For example, desired open window areas were circumscribed with a cutting blade instrument and the coating within the defined area peeled away from the transparent polyester base. In the background areas the resulting master exhibited light transmission of greater than about 25 percent above 6,300 A. and substantially no transmission of light below about 5,800 A. The open window areas of the master transmitted substantially all light between about 4,000 A. and 7,000 A. The master was completed by the application of opaque adhesive transfer lettering through which substantially no visible light was transmitted and the master was employed to expose direct positive photographic material as in example 2.

After light exposure of about 3 minutes to the xenon lamp source as in example 2, the direct positive material was developed, fixed, washed and dried to provide a black image in areas corresponding to the open window and opaque lettered areas of the original.

The above examples have been presented for the purpose of illustration and should not be taken to limit the scope of the present invention. It will be apparent that the described examples are capable of many variations and modifications which are likewise to be included within the scope of the present invention as set forth in the appended claims.

What is claimed is:

l. A method of imaging direct positive photographic material having fogging nuclei, said method consisting essentially of:

a. providing a master bearing features to be reproduced as images on said material, said master consisting essentially 1. a layer of light-filter composition selectively transmissive only of light of wave lengths substantially greater than the peak light sensitivity of said direct positive material,

2. at least one of said features in the form of a lightopaque area substantially wholly nontransmissive of white light, and

3. at least one of said features in the form of an open area in said light-filter layer, said open area being substantially wholly white-light transmissive,

b. positioning said master in overlaying relation upon said direct positive material; and

c. exposing the resulting overlay combination, from the master side, to white light for a time sufficient to destroy the fogging nuclei is said direct positive material in areas underlying solely said light-filter composition layer; and

d. chemically developing the exposed photographic materi- 2. The method according to claim 1 wherein the light-filter layer of said master comprises a transparent support and a readily removable coating thereon of a composition of said selective light-transmissivity.

3. The method according to claim 2 wherein said coating comprises a dispersion of colored pigment in a resinous binder matrix.

4. The method according to claim 2 wherein said coating comprises a film-forming composition of a polymeric resin and a colored pigment. 

2. at least one of said features in the form of a light-opaque area substantially wholly nontransmissive of white light, and
 2. The method according to claim 1 wherein the light-filter layer of said master comprises a transparent support and a readily removable coating thereon of a composition of said selective light-transmissivity.
 3. The method according to claim 2 wherein said coating comprises a dispersion of colored pigment in a resinous binder matrix.
 3. at least one of said features in the form of an open aRea in said light-filter layer, said open area being substantially wholly white-light transmissive, b. positioning said master in overlaying relation upon said direct positive material; and c. exposing the resulting overlay combination, from the master side, to white light for a time sufficient to destroy the fogging nuclei is said direct positive material in areas underlying solely said light-filter composition layer; and d. chemically developing the exposed photographic material.
 4. The method according to claim 2 wherein said coating comprises a film-forming composition of a polymeric resin and a colored pigment. 